Dye loaded zeolite material

ABSTRACT

The present invention provides a dye loaded zeolite material comprising: a) at least one zeolite crystal having straight through uniform channels each having a channel axis parallel to, and a channel width transverse to, a c-axis of crystal unit cells; b) closure molecules having an elongated shape and consisting of a head moiety and a tail moiety, the tail moiety having a longitudinal extension of more than a dimension of the crystal unit cells along the c-axis and the head moiety having a lateral extension that is larger than said channel width and will prevent said head moiety from penetrating into a channel; c) a channel being terminated, in generally plug-like manner, at least at one end thereof located at a surface of the zeolite crystal by a closure molecule hose tail moiety penetrates into said channel and whose head moiety substantially occludes said channel end while projecting over said surface; and d) an essentially linear arrangement of luminescent dye molecules enclosed within a terminated channel adjacent to at least one closure molecule and exhibiting properties related to supramolecular organization.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 11/173,163,filed Jul. 5, 2005, now U.S. Pat. No. 7,372,012, which is a divisionalapplication Ser. No. 10/415,734, filed on May 2, 2003, now U.S. Pat. No.6,932,919, which is a National Stage entry of International ApplicationNo. PCT/CH01/00647, filed Nov. 5, 2001, which claims the benefit of, andincorporates by reference, U.S. Provisional Application No. 60/246,153,filed Nov. 3, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the technical field of opticalmaterials and de-vices. In particular, the invention relates to a dyeloaded zeolite material; the invention further relates to a pigmentmaterial, a luminescent optical device, an optical sensor device, alight emitting device and a photonic energy harvesting device, all theaforesaid comprising a dye loaded zeolite material.

2. Description of the Prior Art

The structural, morphological, physical, and chemical variety ofzeolites has led to applications in different fields like catalysis, ionexchange, membranes, and chemical sensors where dynamic processesinvolving ions or adsorbate molecules play an important role (Thomas, J.M. Spektrum der Wissenschaft, June 1992, 88). Situations where thezeolites mainly serve as host for supramolecular organization ofmolecules, ions, complexes and clusters to prepare materials with newproperties such as non-linear optical (Cox, S. D.; Gier, T. E.; Stucky,G. D. Chem. Mater. 1990, 2, 609), quantum-size (Stucky, G. D.;MacDougall, J. E. Science 1990, 247, 669; Brühwiler, D.; Seifert, R.;Calzaferri, G. J. Phys. Chem. B 1999, 103, 6397), micro laser (Vietze,U.; Krauss, O.; Laeri, F.; Ihnlein, G.; Schüth, F.; Limburg, B.;Abraham, M. Phys. Rev. Lett. 1998, 81, 4628) and artificial antennacharacteristics are new fields of growing interest (Wöhrle, D.;Schulz-Ekloff, G. Adv. Mater. 1994, 6, 875; Schüth, F. Chemie in unsererZeit 1995, 29, 45; Ozin, G. A.; Kuperman, A.; Stein, A. Angew. Chem.1989, 101, 373.).

Some of these new materials can be considered as static and stablearrangements of guests in the zeolite host under a broad range ofconditions (Lainé, P.; Lanz, M.; Calzaferri, G. Inorg. Chem. 1996, 35,3514). In other cases, however, the adsorption, desorption or ionexchange of molecules or ions are reversible processes which lead to awide range of phenomena (Seifert, R.; Kunzmann, A.; Calzaferri, G.Angew. Chem. Inst. Ed. 1998, 37, 1521; Brüwiler, D.; Gfeller, N.;Calzaferri, G. J. Phys. Chem. B 1998, 102, 2923; Ramamurthy, V.;Sanderson, D. R.; Eaton, D. F. J. Am. Chem. Soc. 1993, 115, 10438.).

Plants are masters of efficiently transforming sunlight into energy. Inthis process, every plant leaf acts as a photonic antenna system,wherein photonic energy in the form of sunlight is transported bychlorophyll molecules for the purpose of energy transformation.Accordingly, the synthesis, characterization and possible application ofan artificial photonic antenna for harvesting light within a certainvolume and for transport of the resultant electronic excitation energyto a specific location of molecular size has been the target of researchof several laboratories. Imaginative attempts to build an artificialphotonic antenna have been reported, including multinuclear luminescentmetal complexes, multichromophore cyclodextrines, Langmuir-Blodgettfilms, and dyes in polymers. Sensitization processes in silver halidephotographic materials as well as the spectral sensitization ofsemiconductor oxides also bear in some cases aspects of artificialphotonic antenna systems (“Energy Migration in Dye-Loaded HexagonalMicroporous Crystals”, Gfeller, N.; Calzaferri, G, J. Phys. Chem. B1997, 101, 1396-1408 and references cited therein).

However, to our knowledge, the system reported by us in “Fast EnergyMigration in Pyronine-Loaded Zeolite L Microcrystals”, Gfeller, N.;Megelski, S.; Calzaferri, G. J. Phys. Chem. B 1999, 103, 1250-1257, isthe first artificial photonic antenna that works well enough to deservethis name. In this artificial system, zeolite cylinders are adopted forforming a bi-directional photonic antenna wherein the light transport ismade possible by specifically organized dye molecules that mimic thenatural function of chlorophyll. Zeolites are materials with differentcavity structures. Some of them occur in nature as a component of thesoil. We use zeolite L crystals of cylindrical morphology which consistof a continuous channel system and we have succeeded in filling eachindividual channel with chains of joined but noninteracting dyemolecules. Light shining on the cylinder is first absorbed and theenergy is transported by the dye molecules inside the channels to thecylinder ends (J. Phys. Chem. B 1997, 101, 1396-1408; “Transfer ofElectronic Excitation Energy between Dye Molecules in the Channels ofZeolite L”, Gfeller, N.; Megelski, S.; Calzaferri, G. J. Phys. Chem. B1998, 102, 2433-2436; “Zeolite Microcrystals as Hosts for SupramolecularOrganization of Dye Molecules”, Calzaferri, G. Chimia 1998, 52, 525-532;“Fast Energy Migration in Pyronine-Loaded Zeolite L Microcrystals”,Gfeller, N.; Megelski, S.; Calzaferri, G. J. Phys. Chem B 1999, 103,1250-1257; “Dye Molecules in zeolite L nano crystals for efficient lightharvesting”, Calzaferri, G. in Photofunctional Zeolites, Nova SciencePublishers NY, Editor. M. Anpo, 2000, 205-218; Pauchard, M.; Deveaux,A.; Calzaferri, G. “Dye-Loaded Zeolite L Sandwiches”, CHEMISTRY a Eur.J. 2000, 6, 3456-3470).

We have previously synthesized nanocrystalline zeolite L cylindersranging in length from 300 nm to about 3000 nm. A cylinder of 600 nmconsists of, for example, about 100'000 channels arranged essentiallyparallel to each other. A typical zeolite L material of this kind isshown in FIG. 1. Single molecules of the luminescent dye oxo-nine, whichis capable of emitting light in the red wavelength range, were insertedinto ends of the zeolite's channels that had previously been filled withthe luminescent dye pyronine, which is capable of emitting light in thegreen wavelength range. By means of this arrangement, experimental proofwas furnished that efficient light transport is possible in such zeolitesystems. Light of appropriate wavelength impinging on the zeolite isabsorbed by pyronine molecules only. After such an absorption process,the energy moves along the molecules in the zeolite channel until itreaches a terminal oxonine molecule. The oxonine absorbs the energy by aradiationless energy transfer process, but is not able to send theenergy back to the pyronine. Instead, it emits the energy in the form ofred light, visible to the naked eye.

We have developed two methods for preparing suitable dye loaded zeolitematerials, one method working at a solid/liquid interface and the othermethod working at a solid/gas interface. Other approaches for preparingsimilar materials are in situ and crystallization inclusion synthesis.In our previous work, cationic dyes have been inserted into the channelsof zeolite L via ion exchange from a suspension, thus leading to zeoliteL materials with donor molecules located in the middle and acceptormolecules at the channel ends. After selective electronic excitation ofthe donor molecules, fast energy migration along the c-axis and energytransfer at the channel ends to the acceptor molecules was observed.Subsequently, we have succeeded in preparing three-dye-loaded zeolite Lsandwiches. The general concept of the preparation method of thesematerials is illustrated in FIG. 2 and a selection of molecules thathave been studied is given in FIG. 3. First, a neutral dye molecule isinserted e.g. from the gas phase, filling the channels to the desireddegree. Provided that the inserted molecules are not rapidly displacedby water, this material can then be ion exchanged with a second dye.This can be well controlled, so that a specifically desired space isleft for the third dye, which is either inserted in a next ion exchangeprocess, or from the gas phase. We have shown that by these means abi-directional antenna for light collection and transport can beenprepared so that the whole light spectrum can be used, transportinglight energy from blue to green to red.

Within the context of this work several reactions and equilibria play arole and have been discussed: Insertion reaction of neutral dyes,adsorption at the outer surface, hydration, displacement and reinsertionreactions, and cation exchange. Many data have been obtained forp-terphenyl (pTP). The size of pTP and its chemical properties make itan excellent model for studying relevant parameters and for developingnew preparation methods. The first bi-directional three-dye-zeolite Lsandwich antenna has been realized with DPH as first luminescent dye. Wehave observed that the energy of near UV light that is absorbed in themiddle part of the antenna by DPH is transferred to adjacent pyroninemolecules, i.e. to the second luminescent dye, along which it migratesuntil it reaches the pyronine/oxonine interface, where a further energytransfer occurs from pyronine to oxonine, i.e. to the third luminescentdye (Calzaferri, G.; Brühwiler, D.; Megelski, S.; Pfenniger, M.;Pauchard, M.; Hennessy, B.; Maas, H.; Déveaux, A.; Graf, U. “Playingwith Dye Molecules at the Inner and Outer Surface of Zeolite L”, SolidState Sciences, 2000, Volume 2, 421-447, incorporated herein byreference).

Beyond being usable for a light harvesting system, the principlesdescribed are expected to be exploitable in numerous other applications.However, the dye loaded zeolite materials and any devices made thereofthat have so far been described, exhibit a number of significantshortcomings and disadvantages. In particular, the stability of suchsystems is still unsatisfactory, mainly because of an undesirablemigration of the luminescent dye molecules out of the zeolite channelsresulting in a depletion of the dye loaded zeolite material.

Moreover, the tasks of external trapping of excitation energyor—conversely—of injecting energy at a specific point of the photonicantenna, the realization of a mono-directional photonic antenna and thecoupling of such photonic antennae to specific devices have not beensolved so far.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to overcome theabove discussed shortcomings and disadvantages associated with the dyeloaded zeolite materials and any devices made thereof that have so farbeen described.

In particular, it is an object of this invention to provide a dye loadedzeolite material that is suitable for a wide variety of applications andthat shows improved stability as compared to known dye loaded zeolitematerials.

Further objects of this invention are to provide a pigment materialshowing improved stability, to provide a luminescent optical device, toprovide an optical sensor device, to provide a light emitting device andto provide a photonic energy harvesting device.

According to one aspect of this invention, there is provided a dyeloaded zeolite material comprising:

-   -   a) at least one zeolite crystal having straight through uniform        channels each having a channel axis parallel to, and a channel        width transverse to, a c-axis of crystal unit cells;    -   b) closure molecules having an elongated shape and consisting of        a head moi-ety and a tail moiety, the tail moiety having a        longitudinal extension of more than a dimension of the crystal        unit cells along the c-axis and the head moiety having a lateral        extension that is larger than said channel width and will        prevent said head moiety from penetrating into a channel;    -   c) a channel being terminated, in generally plug-like manner, at        least at one end thereof located at a surface of the zeolite        crystal by a closure molecule whose tail moiety penetrates into        said channel and whose head moiety substantially occludes said        channel end while projecting over said surface; and    -   d) said zeolite material further comprising an essentially        linear arrangement of luminescent dye molecules enclosed within        a terminated channel adjacent to at least one closure molecule        and exhibiting properties related to supramolecular        organization.

According to a further aspect of this invention, there is provided apigment material showing improved stability, comprising a dye loadedzeolite material as set forth hereinabove.

According to another aspect of this invention, there is provided aluminescent optical device comprising a dye loaded zeolite material asset forth hereinabove, wherein said dye molecules are selected such asto have a substantial luminescence quantum yield for a predeterminedexcitation wavelength.

According to a still further aspect of this invention, there is providedan optical device comprising a dye loaded zeolite material as set forthhereinabove, wherein said dye molecules are selected such as to have asubstantial luminescence quantum yield for a predetermined excitationwavelength, and wherein said closure molecule and said dye molecules arecapable of interacting in such manner that an external into fluenceexerted on the head moiety of the closure molecule results in a changeof said luminescence quantum yield.

According to another aspect of this invention, there is provided asegmented dye loaded zeolite material comprising:

-   -   a) at least one zeolite crystal having straight through uniform        channels each having a channel axis parallel to, and a channel        width transverse to, a c-axis of crystal unit cells;    -   b) closure molecules having an elongated shape and consisting of        a head moiety and a tail moiety, the tail moiety having a        longitudinal extension of more than a dimension of the crystal        unit cells along the c-axis and the head moiety having a lateral        extension that is larger than said channel width and will        prevent said head moiety from penetrating into a channel;    -   c) a channel being terminated, in generally plug-like manner, at        least at one end thereof located at a surface of the zeolite        crystal by a closure molecule whose tail moiety penetrates into        said channel and whose head moiety substantially occludes said        channel end while projecting over said surface; and    -   d) an essentially linear arrangement of luminescent dye        molecules enclosed within a terminated channel and exhibiting        properties related to supramolecular organization, said        arrangement comprising at least two segments disposed in a        sequence of adjacent segments, each segment comprising an        essentially linear arrangement of identical dye molecules, at        least one of said segments forming a terminal segment adjacent        at one end thereof to a closure molecule, the dye molecules in        each one of said segments having an optical transition system        comprising an absorption band and an emission band, said        absorption band being generally blue-shifted and said emission        band being generally red-shifted from a nominal wavelength of        the optical transition system, the dye molecules of adjacent        segments having respective optical transition systems in        substantial spectral overlap with each other, said sequence of        adjacent segments being spectrally ordered with respect to said        nominal wavelengths.

The terminal segment may hereby comprise dye molecules with an opticaltransition system in substantial spectral overlap with an opticaltransition system of the closure molecule adjacent to said terminalsegment. The sequence of adjacent segments may also be spectrallyordered with the nominal wavelengths increasing along the sequence awayfrom said terminal segment. The sequence of adjacent segments may, inanother embodiment of this aspect of the invention, be spectrallyordered with the nominal wavelengths decreasing along said sequence awayfrom said terminal segment.

According to yet another aspect of this invention, there is provided alight emitting device comprising a segmented dye loaded zeolite materialas set forth hereinabove, wherein said sequence of adjacent segments isspectrally ordered with said nominal wavelengths increasing along saidsequence away from said terminal segment, said closure molecule and thedye molecules of said terminal segment being capable of interacting insuch manner that energization of the head moiety of the closure moleculeresults in an energy transfer to the optical transition system of thedye molecules of said terminal segment.

The sequence of adjacent segments may hereby comprise an internalsegment separated from said closure molecule by at least one furthersegment. The internal segment may hereby extend along a substantial partof the respective channel.

According to still another aspect of this invention, there is provided aphotonic energy harvesting device comprising a segmented dye loadedzeolite material as set forth hereinabove, wherein said sequence ofadjacent segments is spectrally ordered with said nominal wavelengthsdecreasing along said sequence away from said terminal segment, saidclosure molecule and the dye molecules of said terminal segment beingcapable of interacting in such manner that energization of the opticaltransition system of the dye molecules of said terminal segment resultsin an energy transfer to the head moiety of the closure molecule.

BRIEF DESCRIPTION OF THE DRAWINGS

The above mentioned and other features and objects of this invention andthe manner of achieving them will become more apparent and thisinvention itself will be better understood by reference to the followingdescription of various embodiments of this invention taken inconjunction with the accompanying drawings, wherein:

FIG. 1 is a micrograph showing a Zeolite L material;

FIG. 2 is a scheme illustrating the preparation of a three-dye loadedZeolite L;

FIG. 3 shows examples of luminescent dye molecules that can be insertedin Zeolite L;

FIG. 4 shows relevant structures of Zeolite L and luminescent dyemolecules, namely: left side: a top view of Zeolite L, perpendicular tothe c-axis, displayed as stick-representation (upper panel, FIG. 4 (A))and as Van der Weals representation with an oxonine molecule enteringthe zeolite channel (lower panel, FIG. 4 (C)), and right side: a sideview of a channel along the c-axis, without bridging oxygen atoms (upperpanel, FIG. 4(B)), and the structures of oxonine cation Ox⁺ (top),pyronine cation Py⁺ (middle) and POPOP (bottom) with atom to atomdistances and the coordinate system (lower panel, FIG. 4(D));

FIG. 5 shows structure of typical closure molecules acting as aninjector-, acceptor-, or simply as a stopcock; the positive charge beingdesirable for anionic zeolite hosts and the zero charge being applicablefor all cases;

FIG. 6 shows examples of closure molecules with head moieties that canact as acceptor-heads but also as donor-heads, depending on the type ofdye molecules residing inside of the channels;

FIG. 7 shows further examples of luminescent dye molecules;

FIG. 8 shows examples of segmented dye loaded zeolite systems;

FIG. 9 shows the principle of an inverted antenna system; and

FIG. 10 shows a functionalized bi-directional inverted antenna whichforms the basis of a light emitting device.

The exemplifications set out herein are not to be construed as limitingthe scope of this disclosure or the scope of this invention in anymanner.

DETAILED DESCRIPTION OF THE INVENTION 1. Zeolite Materials

Zeolite materials suitable to act as hosts for supramolecularorganization of molecules, particularly luminescent dye molecules, havebeen described (see references cited in the description of the priorart). The present work is based on the known materials Zeolite L andZeolite ZSM-12. While these nanoporous materials have favorableproperties, they are not, however, the only ones that could be used toproduce the materials and devices described hereinbelow. Nevertheless,we will henceforth concentrate on Zeolite L nano crystals as shown inFIG. 1, noting that an even more homogeneous size distribution as theone shown can be obtained by applying size selective sedimentation.

Said Zeolite L nano crystals exhibiting cylinder morphology havestraight through uniform channels each having a channel axis parallelto, and a channel width transverse to, a c-axis of crystal unit cells.As an essential feature of the present invention, closure molecules areprovided having an elongated shape and consisting of a head moiety and atail moiety, the tail moiety having a longitudinal extension of morethan a dimension of the crystal unit cells along the c-axis and the headmoiety having a lateral extension that is larger than said channel widthand will prevent said head moiety from penetrating into a channel.Accordingly, said channel is terminated, in generally plug-like manner,at least at one end thereof located at a surface of the zeolite crystalby a closure molecule whose tail moiety penetrates into said channel andwhose head moiety substantially occludes said channel end whileprojecting over said surface. Within such terminated channel,luminescent dye molecules are en-closed, forming an essentially lineararrangement and exhibiting properties related to supramolecularorganization.

2. Closure Molecules

A common principle of closure molecules is that they consist of a headmoiety and a tail moiety, the head moiety being too large to enter intoa channel of the zeolite host, whereas the tail moiety can pentetrateinto the end of said channel. Similar to a cork on a sparkling-winebottle, the head moiety substantially occludes in a plug-like manner thechannel end while projecting over a surface of the zeolite crystal.

There are many different embodiments of such closure molecules, whichshould be chosen depending on the specific type of applicationenvisioned and depending on the type of zeolite host material used.

One may distinguish between hosts with an anionic framework such asZeolite L or ZSM-12 and hosts with a neutral framework, such as AlPO₄-5or VPI-5. No substantial difference in respect of these two types ofhost materials arises in those cases where the tail moiety isessentially electroneutral. In contrast, closure molecules with apositively charged tail moiety appear to be particularly interesting inconjunction with anionic hosts such as Zeolite L.

In order to understand the principles and constraints regarding theinteraction between closure molecules and zeolite host, one shouldconsider the relevant structural parameters as shown in FIG. 4. Thegeometrical constraints imposed by the host determine the organizationof the luminescent dye molecules within the channels and further definewhat types of closure molecules are able to fulfill the desiredfunction. The main channels of Zeolite L consist of unit cells with alength of 7.5 Å in the c-direction, as illustrated in FIG. 4. The unitcells are joined by shared 12-membered ring windows having a freediameter of 7.1-7.8 Å. The largest free diameter is about 13 Å,depending on the charge compensating cations. It lies midway between the12-membered rings. The lengths of the primitive vectors a and b are 18.4Å. For example, a zeolite L crystal of 500 nm diameter and 375 nm lengthgives rise to about 67'000 parallel channels, each of which consists of500 unit cells.

The three molecules displayed on the right hand side of FIG. 4illustrate the typical size of molecules that can penetrate into thechannels of zeolite L. However, these molecules are typical only fromthe point of view of their size, not from the point of view of theirproperties, because they do absorb light in the visible or in the nearUV. In contrast, suitable tail moieties typically do not absorb light ofa wavelength longer than about 300 nm.

The general structural characteristics illustrated in FIG. 5 aredesirable for a closure molecule. The diameter h of the head moietiesshould be larger than about 8 Å and the length t of the tail should besuch that it penetrates at least one unit cell (this means 6 Å or morefor zeolite L).

3. Tail Moieties

Tail moieties are generally based on organic or silicon/organicframeworks. Typical tail moieties will not absorb light of a wavelengthlonger than about 300 nm. However, exceptions do exist. Three types oftail moieties play a role, depending on the desired properties: (i) nonreactive tail moieties; (ii) tail moieties that can undergo anisomerization process after insertion in a channel end under theinfluence of irradiation, heat or a reactive species that issufficiently small; (iii) reactive tail moieties that can bind tomolecules inside of the channels. It appears sufficient to provide someexamples of closure molecules with type (i) tail moieties, because forcases (ii) and (iii) a wide spectrum of suitable reactions is known.

4. Head Moieties

Independently of its specific application, any head moiety must be largeenough so that it cannot enter into a channel of the zeolite material.As a consequence of this general condition, any suitable head moietywill also substantially occlude the end of a channel into which therespective tail moiety is inserted, and it will project over the surfaceof the zeolite crystal at which said channel ends. In addition, headmoieties must fulfill any stability criteria imposed by a specificapplication. In general, head moieties will comprise an organic, asilicon-organic or a coordination-type entity.

Advantageously, head moieties are selected so as to achieve a desiredfunctionalization of the dye loaded zeolite's surface properties such asthe wetting ability, the refractive index matching or the reactivity.For example, it might be desirable to select a closure molecule with ahead moiety bearing reactive “arms”, so that after loading the zeolitematerial an additional process could occur, whereby reactive arms ofhead moieties located near the ends of neighbouring channels couldinteract with each other to form a monolayer type polymer at the surfaceof the zeolite crystal.

Particular types of head moieties include acceptor-heads anddonor-heads. Acceptor-heads serve to accept an excitation energytransferred to them by a nearby dye molecule located within the channel.In general, acceptor-heads are strongly luminescent entities having alarge spectral overlap with the dye molecules located inside of thechannels. In contrast, donor-heads must be able to transfer an initiallyreceived excitation energy to a nearby dye molecule located within thechannel. These energy transfer processes are generally radiationless,mostly based on dipole-dipole coupling.

Since luminescence is quenched by dimerization, the head moieties shouldbe prevented from interacting electronically with each other. For thispurpose, it may be necessary to shield a chromophoric part of a headmoiety by attaching to it one or more inactive substituents such asaliphatic groups.

While a large number of chemical entities could be used as headmoieties, practical constraints of various type might limit theselection based on requirements for stability, particular shape,non-toxicity and so forth.

5. Examples of Closure Molecules

A small selection of commercially available molecules suitable asclosure molecules is compiled in FIG. 6, showing, from the top to thebottom:

-   -   6-(((4-(4,4-difluoro-5-(2-thienyl)-4-bora-3a,4a-diaza-s-indacene-3-yl)phenoxy)acetyl)amino)hexanoic        acid succinimidyl ester;    -   a schematic representation of a closure molecule;    -   4,5-difluoro-5,7-diphenyl-4-bora-3a,4a-diaza-s-indacene-3-propionyl        ethylenediamine hydrochloride;    -   “Molecule C”        (benzoxazolium,-[3-[5,6-dichloro-1,3-dihydro-1,3-bis[(4-methylphenyl)methyl]-2H-benzimidazol-2-ylidene]-1-propenyl]-3-methyl-,        chloride (901) (MitoFlour Green); and    -   “Molecule D” (pyridinium,        4-[2-[4-[bis(9,12-octadecadienyl)amino]phenyl]ethenyl]-1-methyl-(9Cl)).

A further compound usable as closure molecule is4-(4-(dilinolethylamino)stiryl)-N-methylpryidinium. Still furtherclosure molecules can be constructed, that comprise a head moiety suchas a substituted porphyrin, a substituted rhodamine, a substitutedruthenium-tris-bipyridine or a substituted C₆₀.

6. Luminescent Dyes

There is a very large number of luminescent dye molecules that aregenerally suited for insertion into the channels of Zeolite L, many ofwhich have been specifically described in the literature citedhereinabove. We will simply mention the molecules shown in FIG. 3, i.e.biphenyl, pyronine, p-terphenyl, oxonine, 1,6-diphenylhexatriene,resorufin, 1,2-bis-(5-methyl-benzoxazol-2yl)-ethene and4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, the latter being alsoknown as Hydroxy-TEMPO. Further suitable luminescent dye molecules arep-bis[2-(5-phenyloxazolyl)]-benzene, also known as POPOP, as well as thedye molecules listed in Table 2 of “Zeolite Microcrystals as Hosts forSupramolecular Organization of Dye Molecules”, Calzaferri, G. Chimia1998, 52, 525-532, which is explicitly incorporated herein by reference.Still further suitable luminescent dye molecules are shown in FIG. 7,which shows, from top to the bottom:

-   -   pyronine G,    -   fluorenone,    -   trans-4-dimethly-amino-4′cyanostilbene,    -   trans-4-acetidinyl-4′-cyanostilbene, and    -   1,4-bis(4-methyl-5-phenyl-2-oxazolyl)-benzene (also known as        dimethyl-POPOP).

7. Dye Loaded Zeolite Materials

In the simplest case, a dye loaded zeolite material as describedhereinabove comprises an essentially linear arrangement of luminescentdye molecules enclosed within a terminated channel. This arrangement isadjacent to at least one closure molecule. By virtue of their specificarrangement resembling a bead chain, a plurality of dye moleculesenclosed within a channel exhibits properties related to supramolecularorganization.

By extension of the principle just described, a segmented dye loadedzeolite material can be envisioned as shown in FIG. 8, wherein anessentially linear arrangement of luminescent dye molecules enclosedwithin a terminated channel and exhibiting properties related tosupramolecular organization comprises at least two segments disposed ina sequence of adjacent segments. Each segment comprises an essentiallylinear arrangement of identical dye molecules. At least one of saidsegments forms a terminal segment that is adjacent at one end thereof toa closure molecule. The dye molecules in each one of said segments havean optical transition system comprising an absorption band and anemission band, said absorption band being generally blue-shifted andsaid emission band being generally red-shifted from a nominal wavelengthλ of the optical transition system. It should be noted that the terms“blue-shifted” and “red-shifted” are to be understood in the sense of“shifted to shorter wavelengths” and “shifted to longer wavelengths”,respectively, as customary in spectroscopy. The dye molecules ofadjacent segments have respective optical transition systems insubstantial spectral overlap with each other, and said sequence ofadjacent segments is spectrally ordered with respect to said nominalwavelengths.

Referring again to FIG. 8, a nano crystal of cylinder morphology with atypical length of 600 nm is divided along its longitudinal channel axisin 3 parts, e.g. with a length of ˜200 nm each. The arrangement labelledas “System 1” in FIG. 8 simply shows the principle of a segmentedarrangement comprising a first segment with dye molecules having anominal wavelength λ₁, a second segment with dye molecules having anominal wavelength λ₂ and a third segment with a dye having a nominalwavelength λ₃, but without showing the respective closure molecules atthe channel end. The dye molecules are preferably strongly luminescentand their nominal wavelengths fulfill the condition λ₁<λ₂<λ₃. Moreover,the spectral overlap integral of the optical transition systems of thedye molecules in adjacent segments is large. In such an arrangement,very fast Förster-type energy migration along the z axis is expected,sup-ported by self-absorption and re-emission processes. The dimensionsof the nano crystal are in the order of the wavelength of the light.

More specifically, “System 2” comprises a closure molecule T placed atthe λ₃-end of the segmented arrangement. Closure molecule T, typically aporphyrine or a phthalocyanine, further acts as an acceptor-head enabledto function as an excitation trap. Conversely, “System 3” comprises aclosure molecule I placed at the λ₁-end of the segmented arrangement andacting as a donor-head capable to function as an energy injector. Asegmented dye loaded zeolite crystal of the type displayed as “System 2”or “System 3” can be connected to a quantum size particle, asemiconductor, a conductor, a conjugated polymer, a quartz fiber and soforth, depending on the application envisaged.

Example 1 Applications of Zeolite Materials Loaded with One Dye

With the dye loaded zeolite materials described hereinabove, it ispossible to produce luminescent dye pigments with extremely highbrilliance and stability. Materials with dye concentrationscorresponding to 0.4 mol/L wherein the dyes are present as monomers andtherefore are very luminescent and brilliant can easily be prepared,covering the whole visible spectrum. Independently of the dye used,these materials are nontoxic since the dye is encapsulated and cannot bereleased to the environment. Particle sizes between about 50 nm to 3000nm can be made, absorptivity and color can easily be tuned, andrefractive index coating is possible. Since the same basic zeolitematerial can be used for a large variety of dyes depending on theparticular application, a large simplification and hence an enormoustechnological advantage is achieved.

As a further application, scintillation materials with extremely highsensitivity and versatility can be prepared with the dye loaded zeolitematerials described hereinabove. It is simple to prepare stable layerson e.g. a plastic material of any shape. Very thin layers (e.g. of a fewhundred nm) with nearly 100% absorptivity can thus be prepared.

Moreover, the dye loaded zeolite materials described hereinabove can beemployed to build novel luminescent optical devices, such as dye laserswith dimensions of a few hundred nanometer, needles for scanning nearfield microscopes and other highly integrated optical devices. Suchdevice could also encompass a highly efficient photosensitizer deviceapplicable, e.g. to photodynamic therapy of malignant tissues. Since theabsorptivity of a 50 nm dye zeolite particle is about 20'000 larger thanthat of a single dye molecules, the treatment could be carried out withmuch lower light intensity, which in some cases could be an importantadvantage.

Example 2 Analytical Probes

Fluorescent molecules are used in many analytical applications inchemistry, biology including cell biology, medicine and environmentalsciences. Many substances specifically designed for such applicationsare available on the market under the general technical term of“fluorescent molecular probes”. In this context, a corresponding termfor the dye loaded zeolite materials described herein would be that of“fluorescent nanoprobes”. In comparison with conventional molecularprobes, said zeolite material can enhance the sensitivity by a factor ofup to about 100'000. Apart from this enormous amplification, nanoprobesbased on the dye loaded zeolite materials according to the presentinvention do not blink, that is, the luminescence signal emitted by themis continuous in time, which has important advantages in someapplications. Such nanoprobes can be made with sizes in the range ofabout 50 nm to 3000 nm, depending on the applications.

The number of unit cells of Zeolite L is given by N_(uc)=0.35 nm⁻³d_(Z)²(nm)I_(Z)(nm) (d_(Z)=diameter of the zeolite, I_(Z)=length of thezeolite, both in nm). Hence, a 100 nm zeolite crystal consists of350'000 unit cells. A typical dye molecule occupies 2 to 3 unit cells.This means that a 100 nm particle contains about 100'000 chromophores(dye molecules). A 50 nm crystal contains correspondingly 43'750 unitcells, which means up to about 20'000 chromophores. Each of them canabsorb a light quantum coming in (this means that the probability ofe.g. a 100 nm dye loaded crystal to absorb a light quantum is 100'000larger than that of a single molecule).

A system for which efficient energy transfer has been found comprises aZeolite L loaded with pyronine cations as dye molecules and providedwith6-(((4-(4,4-difluoro-5-(2-thienyl)-4-bora-3a,4a-diaza-s-indacene-3-yl)phenoxy)acetyl)amino)hexanoicacid succinimidyl ester (i.e. the top molecule in FIG. 6), also known asBODIPY® TR-X SE as closure molecules. Upon illumination with green lightcausing electronic excitation of the entrapped dye molecules, a rapidtransfer of energy to the head moieties of the closure molecules occurs,thus resulting in substantial fluorescence emission in the red spectralregion. It is found that the relative intensity of this red fluorescenceas compared to the intensity of the green fluorescence increases withincreasing concentration of entrapped pyronine dye.

Because of the extremely fast energy migration, we have observed that ina dye loaded zeolite material according to the present invention, it ispossible in favorable cases to quench this luminescence with aprobability of more than 95% by a single molecule undergoing aninteraction with a suitably chosen closure molecule. For example, aclosure molecule can be selected the behavior of which depends on thenature of complexing ions such as H⁺, alkali ions, Ca²⁺, and similar,but also closure molecules the behavior of which depends on localviscosity, local polarity, protein adsorption and other specificinteractions. Indeed, head moieties can be tailored in order to createhighly specific nanoprobes. Such nanoprobes could be used in combinationwith all common techniques, stationary and time resolved, such asconventional fluorescence measurements, standard and unconventionalmicroscopy techniques, fiber optic devices, etc. Optical sensing couldbe applied by monitoring a change of refractive index of an analytesolution in contact with the nanoprobe.

An efficient energy transfer has also been achieved in the oppositedirection, i.e. from the closure molecule to the dye molecules entrappedin the zeolite system. For this purpose, a Zeolite L loaded with oxoninecations as dye molecules was pro-vided with closure molecules consistingof BODIPY® 493/503 SE. Upon illumination with green light causingelectronic excitation of the stopcock molecules, a rapid transfer ofenergy to the entrapped oxonine molecules occurred, thus resulting insubstantial fluorescence emission in the red spectral region.

Example 3 Light Emitting Devices

A segmented dye loaded zeolite material according to the presentinvention can be used to construct a light emitting device, for whichone needs to implement an inverted antenna system. An advantageousfeature of said zeolite materials is that light of any color of thewhole visible spectrum can be generated with basically the samematerial. Spatial resolution can be as low as 100 nm, since the limitsthereto are imposed by the properties of light, i.e. diffraction, not bythe material. We have recently been able to synthesize an invertedantenna system which can be explained by means of FIG. 9. Excitationtravels in a radiationless process from both ends of the crystal towardsthe middle where it is emitted. The amount of blue, green and redemission can be tuned by varying the characteristics, e.g. the length,of the different regions. This means that excitation covering the wholevisible spectrum can be generated by means of basically the samematerial.

Energy supply to the light emitting device occurs as shown in thearrangement of FIG. 10. Initially, a closure molecule provided with adonor-head acting as an injector I is excited, which readily transfersits excitation energy in a radiationless process to the blue dyemolecules in the adjacent terminal segment of the zeolite channel. Fromthere, the inverted antenna transports the excitation energysegment-wise towards the middle of the crystal, where it is finallyreleased as luminescence light. It is sufficient to connect with anexcitation source only one end of the two closure molecules located atopposite ends of a given channel.

It is important to note that with the same injector I and the same bluedye in the terminal segment, light emission of any color can be realizedby just varying the characteristics of the green and the red parts ofthe inverted antenna.

Example 4 Photonic Energy Harvesting Devices

As a further application of segmented dye loaded zeolite systemsaccording to the present invention, a new type of photonic energyharvesting device such as a solar cell can be realized. Such a devicecomprises a sequence of dye segments that is ordered in opposite orderas compared to the light emitting device mentioned hereinabove, and witha closure molecule featuring an acceptor-head. Light absorbed by the dyemolecules in one of the inner segments is efficiently transferred to theterminal segment and then to the closure molecule, from where it couldthen be fed into a suitable energy receiver or consumer system. Theadvantage of such a “dye sensitized solid state solar cell” with respectto current technologies is that in principle very cheap cells with veryhigh efficiency (more than 30% for tandem devices) can be made based onnontoxic materials.

While only the preferred and some typical embodiments of this inventionhave been described hereinabove, it will be understood that theinvention is not limited to the embodiments disclosed, but is equallycapable of numerous other equivalent arrangements, rearrangements,modifications and substitutions of parts and elements, equivalently toachieve the functions, means, ways and results disclosed herein, withoutdeparting from the spirit and teaching of the invention, and areembodied in this invention.

Example 5 Loading of a Cationic Dye into a Zeolite Preloaded with aNeutral Dye

Loading of a cationic dye like pyronine or pyronine G into a zeolitealready loaded with a neutral dye presents the following difficulty.While the cationic dye would usually be added from an aqueous solution,it turns out that water tends to displace any neutral dye moleculespresent in the zeolite, i.e. the neutral dye molecules would be removedfrom the zeolite when attempting to add the cationic dye molecules.Accordingly, it is preferable to use a solvent like 1-butanol, whichdoes not displace the neutral dye molecules from the zeolite. However,it turns out that the ion exchange reaction by means of which a cationicdye molecule entering the zeolite replaces a potassium ion is preventedby the poor solubility of potassium ions in 1-butanol. This problem isovercome by adding to the solution a so-called cryptand, a molecule witha very high affinity for potassium ions.

For example, samples of Zeolite L loaded with pyronine can be preparedby stirring a solution of pyronine in 1-butanol containing a 13-foldexcess of the known cryptand molecule Kryptofix222® and Zeolite L at 50°C. for 44 hours.

1. Dye loaded zeolite material comprising: a) at least one zeolitecrystal having straight through uniform channels each having a channelaxis parallel to, and a channel width transverse to, a c-axis of crystalunit cells; b) closure molecules having an elongated shape andconsisting of a head moiety and a tail moiety, the tail moiety having alongitudinal extension of more than a dimension of the crystal unitcells along the c-axis and the head moiety having a lateral extensionthat is larger than said channel width and will prevent said head moietyfrom penetrating into a channel; c) a channel being terminated, ingenerally plug-like manner, at least at one end thereof located at asurface of the zeolite crystal by a closure molecule whose tail moietypenetrates into said channel and whose head moiety substantiallyoccludes said channel end while projecting over said surface; and d)luminescent dye molecules enclosed within a terminated channel adjacentto at least one closure molecule and exhibiting properties related tosupramolecular organization, wherein said dye molecules are present asmonomers, and wherein said luminescent dye molecules are in essentiallylinear arrangement.
 2. The dye loaded zeolite material of claim 1,wherein said material is non-toxic.
 3. The dye loaded zeolite materialof claims 1, wherein the dye loaded zeolite material has particle sizesbetween 50 and 3000 nm.
 4. The dye loaded zeolite material of claim 1,wherein the material is in form of a stable layer.
 5. Dye loaded zeolitematerial comprising: a) at least one zeolite crystal having straightthrough uniform channels each having a channel axis parallel to, and achannel width transverse to, a c-axis of crystal unit cells; b) closuremolecules having an elongated shape and consisting of a head moiety anda tail moiety, the tail moiety having a longitudinal extension of morethan a dimension of the crystal unit cells along the c-axis and the headmoiety having a lateral extension that is larger than said channel widthand will prevent said head moiety from penetrating into a channel; c) achannel being terminated, in generally plug-like manner, at least at oneend thereof located at a surface of the zeolite crystal by a closuremolecule whose tail moiety penetrates into said channel and whose headmoiety substantially occludes said channel end while projecting oversaid surface; and d) luminescent dye molecules enclosed within aterminated channel adjacent to at least one closure molecule andexhibiting properties related to supramolecular organization, whereinsaid dye molecules are present as monomers, and wherein said luminescentdye molecules are in essentially linear arrangement, wherein thematerial is in form of a stable layer and wherein said stable layer issituated on a plastic material.